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CuS microflowers self-assembled from nanosheets were prepared by hydrothermal synthesis (HS) using CuCl2·2H2O and CS(NH2)2 as raw materials and glycol as a solvent at 120 and 140 °C for 1.5 h. With increasing the hydrothermal temperature or reaction time, the CuS microflowers break up to Cu1.8S nanoparticles. The single phase Cu1.8S nanoparticles were obtained at 200 °C for 10 h. The evolution route of the phase structure and microstructure from CuS to Cu1.8S was investigated. The Cu1.8S particles were densified to bulk materials by applying spark plasma sintering (SPS) technology. The fine-grain bulk Cu1.8S had a Seebeck coefficient of 73 μV K−1 and a thermal conductivity of 1.15 W m−1 K−1 at 673 K, resulting in an enhanced ZT value of 0.49 at 673 K, which is the highest value for pristine Cu1.8S in the literature. Our work indicates that the Cu1.8S system is a potential candidate with low costs and toxicity in mid-temperature thermoelectric application. [ABSTRACT FROM AUTHOR]

Motivated by the recent experimental exfoliation of β-Cu2S thin films and the theoretical finding of a new phase labeled the δ-Cu2S monolayer, we carried out extensive studies on thermal conductivity and thermoelectric properties of the new phase using first principles combined with Boltzmann transport theory, focusing on the analysis of group velocities, Gruneisen parameters, three-phonon scattering rates, and the scattering phase space. Our results show that the δ-Cu2S monolayer exhibits an intrinsically ultralow lattice thermal conductivity of 0.10 W m-1 K-1 at 800 K. Such an ultralow lattice thermal conductivity leads to a high thermoelectric figure of merit ZT = 1.33 at 800 K in an optimum p-type doping concentration, which is not only larger than the value of 1.23 in In2S3 doped Cu2S at 850 K but also comparable with the value of 1.7 in Cu1.97S at 1000 K, exhibiting good potential in thermoelectric applications.

Chalcogenides have been considered as promising thermoelectric materials because of their low cost, nontoxicity, and environmental benignity. In this work, we synthesized a series of Cu 2 S 1- x Te x (0 ≤ x ≤ 1) alloys by a facile, rapid method of mechanical alloying combined with spark plasma sintering process. The Cu 2 S 1- x Te x system provides an excellent vision of the competition between pure phase and phase transformation, entropy-driven solid solution, and enthalpy-driven phase separation. When the Te concentration increases, the Cu 2 S 1- x Te x system changed from the pure monoclinic Cu 2 S at x = 0 to monoclinic Cu 2 S 1- x Te x solid solution at 0.02 ≤ x ≤ 0.06 and then transforms to hexagonal Cu 2 S 1- x Te x solid solution at 0.08 ≤ x ≤ 0.1. The phase separation of hexagonal Cu 2 Te in the hexagonal Cu 2 S matrix occurs at 0.3 ≤ x ≤ 0.7 and finally forms the hexagonal Cu 2 Te at x = 1. Owing to the changed band structure and the coexisted Cu 2 S and Cu 2 Te phases, greatly enhanced power factor was achieved in all Cu 2 S 1- x Te x (0 < x < 1) alloys. Meanwhile, the point defect introduced by the substitution of Te/S atoms strengthened the phonon scattering, resulting in a lowered lattice thermal conductivity in most of these solid solutions. As a consequence, Cu 2 S 0.94 Te 0.06 exhibits a maximum ZT value of 1.18 at 723 K, which is about 3.7 and 14.8 times as compared to the values of pristine Cu 2 S (0.32) and Cu 2 Te (0.08), respectively.

Vaccination is the most effective and cost-effective way to treat hepatitis B virus (HBV) infection. Collective data suggest that helminth infections affect immune responses to some vaccines. Therefore, it is important to reveal the effects of helminth infections on the efficacy of protective vaccines in countries with highly prevalent helminth infections. In the present work, effects of Trichinella spiralis infection on the protective efficacy of HBV vaccine in a mouse model were investigated. This study demonstrated that the enteric stage of T. spiralis infection could inhibit the proliferative response of spleen lymphocytes to hepatitis B surface antigen (HBsAg) and lead to lower levels of anti-HBsAg antibodies, interferon-γ, and interleukin (IL)-2, along with higher levels of IL-4 and IL-5. However, these immunological differences are absent in the muscle stage of T. spiralis infection. The results suggest that the muscle stage of T. spiralis infection does not affect the immune response to HBV vaccination, while the enteric-stage infection results in a reduced immune response to HBsAg.